The invention relates to an electrodeless low-pressure discharge lamp comprising
a lamp vessel which is sealed in a vacuumtight manner, contains ionizable metal vapour and rare gas, and has a cavity at an end portion of said vessel,
an electric coil around a sleeve of synthetic material in the cavity of the lamp vessel,
a tube containing a liquid in the core of soft magnetic material, which tube projects to outside the cavity and has a flange there,
a mounting member which is connected to the sleeve of synthetic material and the lamp vessel and can be fastened against the flange.
Such an electrodeless lamp is known from EP-0 384 520, which corresponds to U.S. Pat. No. 5,006,752.
It is important for the operation of the lamp that the core of soft magnetic material is cooled because its specific magnetic losses increase with increasing temperature and the magnetic permeability starts to decrease at a raised temperature.
The tube containing liquid transfers heat from the core to the flange, while the flange is to transfer heat to its surroundings. Part of these surroundings is formed by a wall, for example of a luminaire, against which the flange of an installed lamp is fastened.
It has been found that a satisfactory cooling of the core in the known lamp is insufficiently safeguarded.